net: hns: use eth_broadcast_addr() to assign broadcast address

mainline inclusion
from mainline-5.9-rc1
commit 74b5afea
category: bugfix
bugzilla: NA
CVE: NA

---------------------------

This patch is to use eth_broadcast_addr() to assign broadcast address
insetad of memset().

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Reviewed-by: li yongxin <liyongxin1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>